This invention relates to a solar energy device and more particularly to a tracker for maintaining itself and another device such as a solar energy cell or collector continuously pointed towards the sun, employing solar energy to provide the moving force.
Solar tracking devices have been known for many years. Sunlight reflectors called heliostats have long been used to maintain a beam of sunlight on a constant direction. The reflectors were rotated by a clockwork or an auxiliary power supply such as an electric motor. Sunlight was used to trigger regulating devices for the external power supply. Aside from additional energy use, electrically powered aiming systems require a power supply with a constant frequency and voltage and a separate feedback path to correct for error.
Of course in many cases, it would be desirable to utilize solar energy to rotate the reflector or other device (termed generally herein the collector) in the proper direction.
While most tracking devices employ external power supplies, a number of devices have been developed which employ solar energy to direct and rotate the collector.
For instance, Geer in U.S. Pat. No. 2,999,943, discloses a device with two sealed jars on either side of a swivel connected by a tube and filled with a volatile liquid. Lord in U.S. Pat. No. 3,231,284, discloses an "S" shaped Bourdon tube for use in a heliotropic (sun following) device. These devices, while effective, are limited in accuracy, responsiveness and in the type of environment in which they may be used.
For example, the device described by Geer is not designed to be sensitive to a slight apparent movement of the sun. There is a lag caused by the time necessary for the liquid to vaporize and recondense; and it relies on gravity to tilt the device.